The invention relates to a process and an arrangement for false-twist spinning in which a sliver is first drafted to the desired size in a drafting unit, subsequently passes through at least one false-twisting nozzle which provides the sliver with a false twist extending back to the drafting unit, and is withdrawn by a withdrawal device arranged behind the false-twisting nozzle.
A process for pneumatic false-twist spinning is described, for example, from the German Patent Document DE-A 37 14 212. In this process, the spreading-away of fiber ends is to be facilitated by the fact that a rotation body is arranged between the pair of delivery rollers of the drafting unit and the false-twisting nozzle, the rotation body having devices for changing the travelling direction of the sliver. As a result, a loosening or opening-up of the fiber structure is to be achieved so that the sliver widens in the transverse direction before entering into the false-twisting nozzle.
It is an object of the invention to provide a process of the initially mentioned type by means of which a yarn can be spun that is as uniform as possible in which a number of fiber ends that is as uniform as possible is wound around the yarn core in a uniform distribution.
This object is achieved in that an air current is applied to the sliver leaving the drafting unit the air current having at least one component that is transverse to the travelling direction of the sliver.
By means of this air current, a relatively large number of fiber ends which will then later be wound around the fiber core can be spread away from the sliver in a relatively uniform distribution.
In an advantageous development of the invention, it is provided that the air current has a component which is directed perpendicularly to the plane of a spinning triangle formed by the sliver at the pair of delivery rollers of the drafting unit. As a result, a large number of fiber ends can be spread away from the sliver.
In a further development, it is provided that the air current also has a component in the travelling direction of the sliver. By means of this measure, it is ensured that the spread-away fibers at first also remain spread away and in this spread-away position are taken along by the continuously travelling sliver.
In a further development of the invention, it is provided that the false twist introduced by the false-twisting nozzle and extending back to the drafting unit is weakened in the area of the sliver which leaves the drafting unit. This extends the length of the spinning triangle in the travelling direction of the yarn so that the spreading-away operation caused by the air current is improved and particularly longer fiber ends can be spread away.
In a further development of the invention, it is provided that fiber ends spread away from the sliver are placed against the sliver in such a way that they wind around it in the area having a false twist by means of a twisting which differs from the false twist. This achieves that the previously spread-away fiber ends, on the one hand, rest against the rotating sliver and do not remain spread-away as a result of centrifugal forces. Because of the twisting of the fiber ends which differs from the false twist of the sliver, the fiber ends, on the other hand, during the subsequent opening-up of the false twist, wind themselves still faster around the sliver so that a yarn is obtained around which the fiber ends are wound. As a result of the fact that the placing of the fiber ends on the sliver is carried out in a controlled manner, a uniform yarn is obtained. In order to implement the placing of the spread-away fibers, it is also provided that the spread-away fiber ends, by means of a guiding device which permits a rotating of the sliver as a result of the false twist are placed on the sliver having a false twist. In order to control the twist by means of which the fiber ends place themselves on the sliver, i.e., wind around it, it is provided in a further development that the guiding device, with at least one movement component, moves in the travelling direction of the sliver. In this case, it is particularly advantageous if it is provided in a further development of the invention that the guiding device takes along the fiber ends in the travelling direction of the sliver at a speed that is increased in comparison to the remaining sliver. As a result, it is achieved that the fiber ends move ahead of the sliver and are wound up with a wind-around direction which is opposite to the false twist so that, when the false twist is later opened up, the wind-around effect is reinforced.
In a further development of the invention, it is provided that the air current is led through the guiding device. As a result, a continuous transition is obtained from the spread-away area to the area in which the fiber ends are placed against the sliver. In this case, it is advantageous for the air current to be generated as a suction air current taken in through the guiding device.
In a further development of the invention, it is provided that the air current, at least in the area facing the drafting unit, flows laterally next to a guiding surface for the sliver. As a result, it is achieved that fiber ends are held separate from the sliver until they are placed against the sliver by means of the guiding surface.
As a development of the invention, an arrangement for false-twist spinning is provided having a drafting unit, at least one following false-twisting nozzle and a withdrawal device, in which devices are provided for generating an air current applied to a sliver leaving the drafting unit, which air current has at least one component which is directed transversely to the travelling direction of the sliver.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.